Restrictions on the availability and increases in the price of petroleum derived fuels and electricity have prompted renewed interest in stoves for burning combustible solid fuels such as wood or coal. So called air-tight stoves which when properly banked will maintain a fire for 8 to 12 hours or more without charging additional fuel have proved objects of particular interest. Known stoves, however, are associated with many shortcomings.
Conventional wood and coal stoves are not very efficient space heaters. Only a fraction of the heat released upon combustion of the fuel is successfully transfered to the room in which the stove is located. Undesirably large proportions of the heat escape with the combustion gases from the stove up the flue.
Wood and coal stoves transfer heat in two ways, by radiation and by convection. Stoves designed for maximum radiant heat transfer usually have a single shell which is heated to a high temperature to radiate heat into the room, but such stoves provide limited convective heat transfer. Stoves developed for efficient convective heat transfer typically are designed with inner and outershells and a blower to force convection air through the space between the shells. The outer shell, however inhibits radiant heat transfer.
The maximum heat output obtainable from most stoves is limited by the natural draft which draws combustion air into the stove, by the size of the stove itself, and by the maximum permissible surface temperature of the stove. Stove surface temperatures can reach 1300 degrees F. or more, but for safe operation should be maintained at sustained temperatures of not more than about 900 degrees F. Because of the high temperatures which the surface of the stove may reach and the large amount of radiant heat transferred from such hot surfaces, stoves typically must be installed some distance away from walls and furniture which could be overheated and ignited. Such installation requirements consume undesirably large amounts of room space.
Stoves provided with electrically driven blower systems to carry heat away from the stove may overheat if the blower is turned off or rendered inoperative by a power outage.
Although substantially all stoves are provided with a damper for regulating the amount of combustion air admitted to the stove, such systems provide only rough control of the heat output of the stove, and in many cases it is difficult to rapidly increase or reduce the heat output of the stove.
Some stoves are provided with windows to enable users of the stove to view a fire within the stove without opening the stove door. An esthetically pleasing view of the fire may still not be obtained, however, because the view of the fire may be blocked by non-burning fuel. Accumulations of soot and dirt on the interior of the window may also obstruct the view of the fire.
In view of the many shortcomings of known wood stoves, there remains a need for an improved stove for burning combustible solid fuels.